03 YZ450 with 13.5 Jetting Issues

I just got done doing a complete rebuild on my bike. I replaced the crank, cylinder, head, valves, springs, retainers, and cams (yamaha oem). I also installed a wiseco 13.5:1 piston in search of more power. The carb has never been apart and is completely stock save for a msr fuel screw. My question is does anyone have any good jetting setup tips or a good baseline to start from? My bike seems to be running incredibly lean. I haven't ridden it yet, only started it a few times to heat cycle it. Any help would be greatly appreciated! Thanks guys.


Even anyone with a setup similar to mine would be helpful. Or at least a hint as to what changes I will need to make. I am assuming I will need to richen up the main, but I am not sure about the pilot. Any help would be appreciated.

Why do you say it's lean?

Because it is backfiring really hard when I let off the throttle, and typically shoots a 3-4" flame out the exhaust when it does this. I have tried adjusting my fuel screw, but have had no luck getting the backfire to go away.

Check the exhaust system for air leaks first. If you are convinced that there are none, then go up a step on the pilot jet.

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